Ordered organopolysiloxanes



United States Patent Office 3,378,521 Patented Apr. 16, 1968 ABSTRACT OFTHE DISQLOSURE Organopolysiloxane-alkanol amine copolymers and blockorganopolysiloxane-oxyalkylene amine copolymers having the generalformula where R is a monovalent hydrocarbon radical, R is an alkyleneradical of from to 1 carbon atoihs, or an arylene radical containing upto 20 carbon atoms, R" and R are organic radicals free ofaliphatic-substituted halogen and are members of the class consisting ofmonovalent hydrocarbon radicals, cyanoalkyl radicals, and halogenatedaryl radicals, m is a whole number from 0 to 2 inclusive, x is aninterger having a value of at least 1 and y is an integer having a valueof 0, l or more, are produced by forming an admixture of (a) anorgano-lithium compound of the formula where R, R and m are aspreviously defined with (b) a cyclic siloxane of the formula Till ' La Iwhere R is as above-defined and need not represent the same entity onthe same silicon atom, is added and the mixture heated to cause reactionof the copolymer with the second cyclic siloxane to produce theblock-block copolymer of Formula I, wherein x and y are integers havingvalues of at least 1. The copolymers of Formula I are useful asdielectric fluids, lubricants, foam additives, etc.

lib

This application is a continuation-in-part of my application Ser. No.541,539, filed Apr. 11, 1966, now abancloned.

This invention relates to sequentially arranged preordained blockcopolymers in which at least 75% or more and up to close to 100%, of theblocks in the polymer are of a pre-ordained and regular nature and arederived in essentially the same order and the same relative amount asthe cyclic organotrisiloxane employed for making the aforesaid polymer.I

The polymers of Formula A can be further reacted as hereinafter setforth to produce polymers end-blocked with various groups. Thus, forexample, the novel compositions produced in accordance with thisinvention are represented generically by the formula wherein R, R, R",R, m, x and y are as above defined and M is lithium, hydrogen, acyl ororganosilyl.

The term aprotic solven is intended to mean any organic solvent whichhas no active protons which may interfere with growing anionicpolymerization centers. As will be evident to those skilled in the art,any aprotic solvent which is capable of dissolving the polymeric mixtureand causing intimate contact of an additional diorganocyclosiloxane withthe polymerizing system may be used. These may include such solvents asbenzene, toluene, xylene, mesitylene, etc. The use of solvents havingdifferent boiling points allows the practice of this invention atvariable temperatures. However, it is preferred that certain specialdipolar aprotic solvents having electron-donating centers be employed.These solvents are chosen such that their electron-donating centers arecapable of forming coordinated complexes with the lithium cation,thereby increasing its reactivity towards dior-ganocyclosiloxanepolymerization without the loss of specificity in ring openingreactions. Aprotic solvents which have Lewis base characteristics arepreferably employed because of their ability to donate electrons to thelithium cation, which thereby coordinates with the lithium and enhancesits reactivity by virtue of such coordination.

It is known in organosilicon art that cyclic diorganosiloxanes could bepolymerized to high polymers by heating them with alkaline catalysts,such as potassium hydroxide or its corresponding siloxane salts. Thishas become the predominant method for the production of siloxaneelastomers. However, during this alklaline polymerization, breaking ofthe siloxane ring to form high polymers and degradation of high polymersto form cyclics is occurring constantly, and since these polymerizationand degradation reactions occur at different rates, the resultingproduct represents an equilibrium between the two processes. Because ofthese competing reactions, any polymer which is ultimately formed, ifproduced from a mixture of cyclic polysiloxanes, contains a randomdistribution of the segments derived from the different cyclicpolysiloxanes involved. These polymers (which term is intended toinclude copolymers, terpolymers and more complex mixtures of siloxaneunits) although exhibiting useful properties, due primarily to theirgross composition of matter, are highly random in nature. Thisrandomness is often aggravated during copolymerization of two or moreorganocyclopolysiloxanes by the difference in reactivity of thecyclopolysiloxanes. In addition, it is often diflicult to obtainpolymerization without significant formation of cyclic polysiloxanesresulting in an undesirable contamination of the finally polymerizedproduct.

Workers in the silicone art have made numerous attempts to reduce oreliminate this randomness in the hope of better controlling thepolymerization and condensation reaction. One of the methods forsynthesizing organosiloxane block polymers is based on the premise thatthe homopolymer segments must be prepared separately and then coupled bymeans of an appropriate condensation catalyst. For instance, in U.S.Patent 3,156,668, issued Nov. 10, 1964, hydroxy chain-stoppedpolydiorganosiloxanes of the formula where R has the meaning above and nis a whole number in excess of 1, are heated in the presence of, forexample, lithium hydroxide or a lithium silanolate as catalyst to effectcondensation of the hydroxy groups and to lengthen the chain. Althoughthis process is intended to minimize the formation of cyclicpolysiloxanes, nevertheless, it is apparent that if two differenthydroxy chain-stopped polydiorganopolysiloxanes are interacted by thismethod, the manner in which these polymers will intercondense will againbe of a random nature by virtue of the inability to control the pointsat which each siloxane segment will attach to its neighboring siloxanesegment, thus allowing intracondensation as well as intercondensation ofsiloxane segments. Furthermore, this again leads to the undesirableformation of cyclic polysiloxanes as contaminants and as a limitingfactor on the optimum yield of linear polysiloxanes. As a furtherlimitation on this process, the segments must be difunctional and ofhigh purity in order to attain gel-free, high molecular weight, linearpolymers. For the foregoing reasons, the ultimate structure andproperties of such copolysiloxanes are still difiicult to define and mayvary widely with slight differences in segment length and reactivity,and preparative conditions.

I have now discovered a means for making block-block copolymerssequentially arranged in a preordained manner by employing theabove-described organo-lithium compound with a cyclic organo-trisiloxaneusing a particular class of solvents for the purpose. In addition tobeing able to prepare organopolysiloxanes having extremely narrowmolecular weight distributions, it has also been possible to effectfurther polymerization without equilibration, i.e., without any siloxanerearrangement. Thus, once polymer chains are formed, because of theirstability to the basic lithium ion, they do not undergo significantequilibration or rearrangement. In addition, by virtue of the highdegree of order present in the polymer, the latter have new and uniqueproperties of an unpredictable nature. By means of my process, one canperform custom synthesis of block copolymers, and the properties of thepolymer can be varied by the choice of the organopolysiloxane, thesegment length, the sequence of segments, and gross molecular weight.

In referring to the blocks comprising the polymers prepared inaccordance with the practice of the present invention, it is intendedthat these blocks include not only single diorganosiloxy trimeric units.

but also a plurality of diorganosiloxy trimeric units linked to eachother directly through the oxygen atom. These preordained blocks ofdiorganosiloxy trimeric units also include from 1 to as many as a 1000or more trimeric siloxy units derived from the lithium compound.Additionally, by sequentially adding various cyclotrisiloxanes, one canintroduce blocks of diorganosiloxy trimeric units of many varietiesthereby further modifying the properties of the ultimate products.

The fact that I have been able to produce the abovedesired sequentialblock-block copolymers by means of the above-described process wasentirely unexpected and in no way could have been predicted. In thefirst place, it is important that one employ the above-describedorganolithium compound. When one employs, for example, otheralkali-metal compounds in which the lithium atom or atoms of thecompound of Formula I is replaced by potassium, any reaction whichoccurs will lead to equilibrated and random products rather than thepre-ordained, regular block-block copolymers.

It should be recognized that the method of growth of the block polymercan be unidirectional, or can proceed in two or as high as threedirections depending on the number of lithium atoms in theorgauo-lithium compound. For instance, if one were to reacthexamethylcyclotrisiloxane with an organo-lithium compound having theformula in the aprotic solvent, one would obtain a compositioncorresponding to the formula If one employs a molar ratio of one mole ofthe abovedescribed organo-lithium compound of Fonmula III per threemoles of the hexamethylcyclotrisiloxane, one introduces ninedimethylsiloxy units into the organo-lithium compound yielding acomposition having the formula Lie. .1.

Thus, by Working with the previously prepared organolithium compound,and using multiples of the cyclotrisiloxane, one can form alithium-containing polymer, which in addition to having in the polymerthe residue from the organo-lithium compound, would also have multiplesof the three siloxy groups from the cyclic trisiloxane, the multiplesdepending on the molar ratio of the trisiloxane to the organo-lithiumcompound.

Other blocks can then be added on to the polymer of Formula IV. Forinstance, the latter composition in the aprotic solvent can be furtherreacted under the same conditions as previously, with hexaphenylcyclotrisiloxane, to give a lithium compound of the formula Lhml. L5H.1.

Obviously this interaction with various cyclic trisiloxanes can becontinued indefinitely, each time introducing a different segment, if sodesired, in a predetermined position to give a pre-ordained tailoredpolymer in which essentially all the blocks are in the same sequence andamount as the order and molar concentration in which the cyclicpolysiloxane is added.

As a further illustration, one can react in an aprotic electron-donatingsolvent at low temperatures, for instance, the organo-lithium compoundof Formula III with trimethyltriphenylcyclotrisiloxane to give acomposition of the following structure:

Lal.

where w is the number of moles of the cyclotrisiloxane per mole of theorgano-lithium compound.

In addition to the organo-lithium compound being one which has a singlelithium atom, one can also employ lithium compounds containing two orthree lithium atoms of the type described in Formula I. By the use ofsuch dior trilithium compounds, one can effect growth on two or threesides of the units attached to the lithium atoms. Glasses of polylithiumcompounds effective in the practice of the present invention can berepresented generically by the formulas where R and R have the meaningsgiven above. Specific examples of dilithium and trilithium compounds inaddition to monolithium compounds employed in the practice of thepresent invention are recited below:

(X) CH N-(CH CH -O-Li) (XI) (CI-I --NCH CI-I -O-Li C H N-( C H O-Li 2 (CH -N-CH -CH CH OLi The organo-lithium compounds recited above can thenbe reacted with cyclotrisiloxanes containing different silicon-bondedorganic groups (e.g., hexaphenylcyclotrisiloxane,hcxamethylcyclotrisiloxane, trimethyltriphenylcyclotrisiloxane,including the latters various isomers, hexamethylcyclotrisiloxane, etc.)to give linear or branched, ordered, block-block copolymers containingresidues from the organo-lithium compound and also siloxane unitsderived from the cyclotrisiloxane. For example, if one uses according tomy process equal molar amounts of hexaphenylcyclotrisiloxane and anorganolithium compound of Formula XI, a composition of the XIII isobtained; with the dilithium compound of Formula X one obtains withhexaphenylcyclotrisiloxane a composition of the formula Finally, if onereacts the organo-lithium compound of Formula XII, withhexaphenylcyclotrisiloxane, one obtains a composition of formula Oncethe above-described lithium silox-anolates have been formed, the lattercan be further reacted if desired with other cyclotrisiloxanes for thepurpose of combining additional trisiloxane units or multiples thereofto further lengthen the chain. It should be noted that once the initialreaction has taken place between the organolithium compound and thefirst cyclotrisiloxane, it is possible to interactdiorganocyclotetrasiloxanes (for example,tetramethyltetraphenylcyclotetrasiloxane) more readily than if thecyclotetrasiloxane is attempted first to be reacted with theorgano-lithium compound. Although there is still danger of somerandomness being introduced into the polysiloxane by virtue of the useof the tetrasiloxane as contrasted to the highly ordered result obtainedby using the cyclotrisiloxane, nevertheless, the intercession of thefirst cyclotrisiloxane reaction with the organo-lithium compoundmaterially reduces the randomness effect occasioned by the furtherinteraction with the cyclotetrasiloxane.

Among the members which R, R" and R' may be in the foregoing Formulas A,I, 11a, 11b and B are, for instance, alkyl radicals (e.g., methyl,ethyl, propyl, isobutyl, hexyl, etc.); aryl radicals (e.g., phenylnaphthyl biphenylyl etc.); aralkyl radicals (e.g., benzyl, phenylethyl,etc); alkaryl radicals (e.g., tolyl, xylyl, ethylphenyl, etc); alkenylradicals (e.g., vinyl allyl, methallyl, etc); halogenated aryl radicals(e.g., chlorophenyl, tetra chlorophenyl, chloronaphthyl,tetr-afluorophenyl, etc); cyanoalkyl radicals (e.g., cyanoethyl,cyanopropyl, cyanobutyl, etc.); etc. The presence of halogens,particularly fluorine, on an aliphatic carbon attached to silicon in thecyclic polysiloxane in Formula Hz: or IIb markedly increases thetendency of the cyclic trisiloxane to form random polymers, thusdefeating the purpose of the present invention to maximize the orderedarrangement of units in the formal organopolysiloxane. This precautionof avoiding the presence of halogen or aliphatic carbon does not applyto the radicals which R represents. Accordingly, organo lithiumcompounds, for instance, of the formulas etc., can be used for reactionwith the cyclic polysiloxane of Formula II.

The organo-lithium compounds of Formula I can be produced in any one ofmany well known methods. For example, one can mix at least one mole oflithium hydroxide and one mole of an organonitrogen compoundcorresponding to formula here R, R, and m have the meanings given above.By heating the mixture at about 50 to 70 C. for about /2 hour to 8hours, one is able to obtain the desired organolithium compound.Alternatively, instead of lithium hydroxide one can employ lithium metalfor making the organo-lithium com-pound. As a specific example, one caneffect reaction between lithium hydroxide and a stoichiometric amount ofeither triethanolamine, N-methyl diethanolamine, N,N-dimethylethanolamine, etc., with lithium hydroxide to form organo-lithiumcompounds generically represented by Formula I.

Among the preferred aprotic solvents which may be employed in thepractice of this invention are non-acid oxygen-containing andnitrogen-containing organic solvents capable of coordinating with thelithium. These include, for instance, tetrahydrofuran (hereinafterreferred to as THF), tetrahydropyrane, diethoxyethane, dimethoxyethane,dimethyl ether of diethylene glycol, N,N- dimethyl acetamide,N-methylpyrollidone, isobutylene oxide, dimethyl sulfoxide, dioxane,diethyl ether of diethylene glycol, various tertiary amines such as, forinstance, dimethyl aniline, tributyl amine, pyridine etc. Solvents whichcontain active hydrogen or an acid hydrogen should be avoided because ofthe reactivity of the lithium with the acidic hydrogen to produce newreaction centers and thereby causing a randomness in the mixture andreducing blocking or order contrary to the intent of this invention.

The fact that such electron-donating solvents react so effectively withthe organo-lithium compound was totally unexpected and in no way couldhave been predicted since the prior art teaches that lithium ions arehighly solvated by the above-described media and makes no referenceordistinction between lithium and other alkalimetal atoms thus leadingto the expectation, contrary to my discovery, that lithium would reactin a random fashion similar to that encountered when employing, e.g.,sodium, potassium, etc., ions.

The manner in which my invention may be practiced may be varied Widely.Thus, the organo-lithium compound is reacted with theorganocyclotrisiloxane, preferably in the presence of the aproticsolvent, employing tempera- 7 tures which vary over wide ranges, forinstance from about -50 C. to 250 C. or higher. It is preferred that theinitial reaction between the organo-lithium compound and thecyclotrisiloxane be at temperatures below about 200 C. When an electrondonating solvent is employed, temperatures as low as 50 C. may beemployed. This initial reaction can take place in a time ranging fromabout minutes to as much as 2 hours or more depending upon such factorsas the temperatures employed, the organo-lithium compound used, theparticular cyclotrisiloxane, the molar concentrations of theorgano-lithium compound and of the cyclotrisiloxane, etc. Thereafter, ifit is desired to add on other organosiloxane units to the backbone ofthe siloxane unit already prepared, one can incorporate in the reactionmixture (employing the same aprotic solvent) whatever otherorganocyclotrisiloxane is desired for the purpose and in theconcentration intended to give the type of product sought. Theconditions of addition and reaction are essentially the same as those ofthe initial organo-lithium compound and cyclotrisiloxane except that insucceeding reactions, temperatures in the order of from 50 to 250 C. areadvantageously employed in order to drive the reaction to completion. Inall circumstances, anhydrous conditions should be observed, and theexclusion of oxygen by means of an inert atmosphere (e.g., nitrogen,helium, etc.) is advantageously employed.

By means of this sequential addition of the various cyclotrisiloxanes,one can build polymers of any desired length predicting in advance therepetitive unit present in the polymer, its position in the polymer, andthe length of the repetitive unit. The length of each segment may bepredesigned and will be integrally multiplied in accordance with themolar concentration and the cyclotrisiloxane reacted with theorganolithium compound or with successive block polymer reactions moreparticularly described above.

This ability to predesign polymers and carry out the actual preparationsof such polymers allows one to obtain products having unusualcharacteristics of solubility, heat resistance, crystallinity, improvedtoughness, flexibility, low temperature flexibility, etc. Quite apartfrom what might have been predicted from previously prepared copolymers,whereas previous random type polymers made by the polymerization of twocyclic trisiloxanes with materials, such as potassium hydroxide, are ofa random type and are soluble in aromatic hydrocarbons such as benzeneand toluene, at room temperature, the highly ordered polymers preparedin accordance with my process are relatively insoluble in these solventsand require solvents such as diphenyl ether, or 2,4-dichloroanisole atelevated temperatures (for example, 125 to 225 C.) for solubilization.This resistance to solvents is believed due to the crystallinity of theformed polymers. Polymers of this invention show a variation incrystalline melting points for the diflerent organosiloxy segments.

The lithium block copolymers derived from the reaction of theorgan0-lithium compound and one or more cyclotrisiloxanes can be treatedin various ways to obtain an organopolysiloxane free of lithium atoms.Thus, the final lithium polymer can be reacted with water or carboxylicacid, such as acetic acid, propionic acid, etc., to replace the lithiumatom with a hydrogen atom to form a hydroxyl-terminated polysiloxane.One can terminate the block copolymers with an acyloxy group by reactingthe lithium block copolymers with a diacylanhydride such as aceticanhydride, butyric anhydride, phthalic anhydride, benzoic anhydride,etc., and acid chlorides such as acetyl chloride, propanoyl chloride,benzoyl chloride, etc. Alternatively, it one wishes to have atriorganosilane or similar terminating organosilicon group, one canreact the lithium atom of the finally obtained lithium polymer with, forinstance, a triorganohalogenosilane, such as trimethylchlorosilane,triphenylchlorosilane, etc., to obtain lithium chloride and achain-terminating triorganosilyl group. This can lead to stable fluidshaving unusual characteristics, especially if highly isotacticstructures in excess of 65% isotacticity is present as a result of beingable to maintain the high degree of isotacticity from reaction of theorganolithium compound and acis-2,3,6-trimethyl-2,4,6-triphenylcyclotrisiloxane. To insure completeremoval of the glacial acetic acid from the polymer, a wash withmethanol, particularly with a to 10 percent, by weight, mixture ofmethanol and water, will remove any residual glacial acetic acid whichmay be present in the polymer.

In order that those skilled in the art may better understand how thepresent invention may be practiced the following examples are given byWay of illustration and not by way of limitation. Unless otherwisestated all parts and percents are by weight. In each instance unlessindicated otherwise, the reaction was conducted under substantiallyanhydrous conditions and under an inert atmosphere, such as nitrogen.

EXAMPLE 1 Two hundred ml. (0.3 mole) n-butyllithium in n-hexane togetherwith 50 ml. benzene and 50 ml. diethylether was added slowly to 13.3 ml.(0.1 mole) triethanolamine and the reaction mixture was stirred forabout one hour after which the precipitate which formed was allowed tosettle. The supernatant liquid was removed and the solid precipitate waswashed twice with benzene, dried to give 15.1 grams of the compound(XVI) (LiOC H N melting at 195-215" C.

EXAMPLE 2 tively, used:

t ed Ll-o-st-o-clul N XVII L s .Jsx a This polymer could be treated withabout 3 moles of trimethylchlorosilane per mole of the polymer FormulaXVII to give a chain-stopped organopolysiloxane of the formula L (1311:|ax a together with lithum chloride.

EXAMPLE 3 A block-block copolymer was prepared from the organolithiumpolysiloxane composition of the Formula XVII in Example 2 by effectingreaction between 5 grams of hexaphenylcyclotrisiloxane dissolved in 30ml. benzene and the reaction mixture (including THF solvent) obtained inExample 2 from the reaction of the hexamethylcyclotrisiloxane with thelithium salt of the triethanolamine. The mixture of ingredients washeated at the reflux temperature of the mass for about 30 minutes duringwhich solvent was removed under a nitrogen screen. Thereafter, thereaction mixture was subsequently heated C. for 30 minutes and at about200 C. for four hours. This yielded a branched block-block copolymerhaving the formula By treating this polymer with acetic acid or aceticanhydride, the lithium atoms could be removed to yield a hydroxychain-stopped polysiloxane of the formula l L .l L 115 3y CH3 3: 3

EXAMPLE 4 The dilithium salt of N-methyl-diethanolamine corresponding tothe formula is prepared similarly as in Example 1 with the exceptionthat instead of using triethanolamine, N-methyl-diethanolamine isreacted with the n-butyllithium. Employing the conditions recited inExamples 2 and 3, 5 grams hexamethylcyclotrisiloxane is first reactedwith the dilithium salt of Formula XXI in 2 ml. of dry tetrahydrofuranand thereafter the product formed is reacted with 5 grams ofhexaphenylcyclotrisiloxane, again employing the conditions of Example 3.This produces a block-block copolymer corresponding to the formula XXIIL .H.l..L tel.

The composition of Formula XII can be treated to remove the lithiumatoms and to replace one or both with a triorganosilyl group, hydrogen,or other organosilicon moieties in accordance with the various methodsdescribed above.

EXAMPLE 5 The monolithium salt of N,N-dimethyl-ethanolaminecorresponding to the formula L t.H.l.L tel...

where q is equal to the number of moles of the methylphenyl trimer used.

The composition of Formula XXIV can be treated to remove the lithiumatom and to replace it with a triorganosilyl group, hydrogen or otherorganosilicon moiety in accordance with the various directions recitedpreviously.

EXAMPLE 6 About 3.34 grams of the lithium salt prepared in Example 1(having the Formula XVI) was suspended in 150 m1. dry freshly distilledtetrahydrofuran, and thereafter 26.6 grams (0.12 mole)hexamethylcyclotrisiloxane was added with stirring under a nitrogenblanket for 6 hours while the mixture was heated at its refluxtemperature. The reaction mixture was filtered and the filtrate wasevaporated to an oily liquid, redissolved in benzene, washed with waterand the organic layer separated. The

organic layer was dried and a fluid polymer obtained which had theaverage general formula This polymer was found to have a molecularweight in benzene of approximately 1240. This fluid had a decidedtendency to stabilize and initiate the formation of foam. Thus, when afew drops of this fluid were added to a benzene-Water emulsion, it wasfound that the emulsion was stable for as long as 4 days with thispolymer present. In the absence of this polymer, the emulsion separatedwithin a few hours. This polymer is therefore useful as a surfactant inthe making of polyurethane foams.

The polymers prepared in accordance with the practice of my inventionhave unique and unexpected properties.

They can be readily differentiated from prior art compositions even fromcompositions which were obtained by methods intended to introduce blockcopolymers. In the first place polymers obtained by means of my process(whether with the lithium atoms or with the lithium atoms replaced) canhave at least 98% and closer to 100% pre-ordained regularity of theblock segments in the polymer as contrasted to the much lowerpre-ordained block segments of a regular nature possible by means of theprior art methods for making block copolymers. In addition, the productsof my invention have unusual strengths and elonga-t-ions, even in theunfilled state, when converted to the cured condition by means ofcrosslinking agents normally employed for the purpose, such as, benzoylperoxide, di-(a-cumyDperoxide, tertiary butyl perbenzoate, etc. Thecrystallinity introduced by means of the regularity of the polymersherein prepared again imparts a unique characteristic which is not foundto the best of my knowledge in polymers of comparable organosiloxanecontent in the prior art. In particular the insolubility of my polymerseven in the uncured state renders them unique in contrast to prior artpolymers which exhibit ready solvation characteristics in usual solventssuch as benzene, toluene, etc. This insolubility can be translated intoimproved resistance to swelling in hydrocarbon solvents when thesepolymers are converted to the infusible, insoluble state by peroxidecuring or even by high energy radiation, for instance, high energyelectrons.

The ability to obtain unequivocal synthesis of the block copolymers oforganocyclosiloxaues results in the attainment of both crystalline andamorphous block segments in a polymer chain, the crystalline segmentscontributing to solvent resistant, high temperature stability, andtensile strength, while the amorphous segments allow low temperatureflexibility or extensibility. These bulk properties can be changed byprevious thermal or solvent treatment.

The compositions of the present invention, particularly those in whichthe lithium atom has been removed and substituted with, for instance,hydrogen, triorganosilyl group, or some other organosilicon moiety, havemany uses. They can be mixed with various fillers such as finely dividedsilica, carbon black, etc., and then crosslinked either by organicperoxides with which organopolysiloxane elastomers are usually cured, orwith high energy radiation, as more particularly disclosed and claimedin US. Patent 2,763,609, issued Sept. 18, 1965, and assigned to the sameassignee as the present invention. In the cured state, these polymerscan be used for insulation purposes, for insulating electricalconductors, as encapsulating agents, in capacitors, and as coatings forsurfaces which require resistance to moisture and to heat. By the properchoice of organosiloxane units in the polymers, it is possible to makefluids which can be employed as dielectric fluids, in lubricating media,etc. Alternatively the polymers, particularly those free of the lithiumatom, can be used for control of foam in liquids which normally aresusceptible to foaming. Those organopolysiloxanes containing terminalsilicon-bonded hydroxyl groups can be further condensed by dehydratingagents or by organemetallic compounds such as iron octoate to givefurther lengthening of the chains through the medium of the silanolgroup. In this respect, the hydroxy chain-stopped polysiloxane can beused as an ingredient in making room temperature vulcanizingcompositions as is more particularly disclosed in US. Patent 2,843,555,Berridge, assigned to the same assignee as the present invention.

It will, of course, be apparent to those skilled in the art thatmodification other than those set forth in the above examples can beemployed in the process of this invention without departing from thescope thereof.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The process for producing organopolysiloxane copolymers of theformula where R is :a monovalent hydrocarbon radical, R is an alkyleneradical of from 1 to carbon atoms, or an arylene radical containing from6 to carbon atoms, R" is an organic radical free ofaliphatic-substituted halogen and is a member selected from the classconsisting of monovalent hydrocarbon radicals, cyanoalkyl radicals, andhalogenated aryl radicals, x is an integer having a value of at least 1,and m is a whole number equal to from 0 to 2 inclusive, which comprisesforming an admixture of an aprotic solvent, an organo-lithiurn compoundcorresponding to the formula (R) (R'O-Li) and a cyclic polysiloxane ofthe formula lilol Li I Ll I

wherein R is an organic radical free of aliphatic-substituted halogenand is a member selected from the class consisting of monovalenthydrocarbon radicals, cyanoalkyl radicals and halogenated aryl radicals,said second cyclic siloxane being different from the cyclic siloxaneemployed in claim 1, is added to the reaction product of claim 1, underanhydrous conditions and the resulting mixture maintained at atemperature at which said second cyclic siloxane and said reactionproduct of claim 1 react to produce a block block organopolysiloxane ofthe formula wherein R' is as above-defined, R is a monovalenthydrocarbon radical, R is an alkylene radical of from 1 to 10 carbonatoms or an arylene radical containing from 6 to 20 carbon atoms, R" isan organic radical free of aliphatic substituted halogen and is a memberof the class consisting of monovalent hydrocarbon radicals, cyanoalkylradicals and halogenated ar-yl radicals, x is an integer of at least 1,y is an integer of at least 1 and m is an integer of from 0 to 2inclusive.

4. The process as in claim 3, wherein the product produced is treated soas to produce a polymer chainstopped with a member of the classconsisting of hydrogen, organosilyl and acyloxy groups.

5. The process as in claim 1 in which the organolit-hium compoundcorresponds to the formula (Li-O--C H N and the cyclic polysiloxane is'hexamethylcyclotrisiloxane.

6. The process as in claim 3 in which the reaction product of claim 1has the formula wherein x is an integer having a value of at least 1,and the second cyclic polysiloxane is hexaphenylcyclotrisiloxane.

7. The process as in claim 1 in which the organolithium compoundcorresponds to the formula and the cyclic polysiloxane ishexamethylcyclotrisiloxane. 8. A composition of matter having thegeneral formula where R is a monovalent hydrocarbon radical, R is analkylene radical of from 1 to 10 carbon atoms or an arylene radicalcontaining up to 20 carbon atoms, R" and R are organic radicals free ofaliphatic-substituted halogen and are members of the class consisting ofmonovalent hydrocarbon radicals, cyanoalkyl radicals and halogenatedaryl radicals, M is a member of the class consisting of lithium,hydrogen, acyl and organosilyl, m is a whole number from 0 to 2inclusive, x is an integer having a value of at least 1 and y is aninteger having a value of 0, 1 or more.

9. A composition as in claim 8 wherein M is lithium.

10. A composition as in claim 8 wherein M is a trimethylsilyl group.

References Cited UNITED STATES PATENTS 3,337,494 8/1967 Bostick260--46.5

DONALD E. CZAJA, Primary Examiner.

M. I. MARQUIS, Assistant Examiner.

